fuel tank sealing - sloshing

[Pascal 29]

the unfinished avid model c i've taken over already has its wings covered and painted but the fuel tanks are still unused. in the local EAS (=EAA in the us) chapter a guy recommended i should clean the tanks with acetone and then seal them with some 2 component fuel tank sealant in order to make the fueltanks resistant against fuel that contains ethanol. around here in europe "mogas" can differ from airstrip to airstrip and especially out in the country side there is often some type of car-fuel that might contain ethanol as well and i want to be able to use that stuff as it makes flying around the more remote strips in italy and other european countries so much easier if you don't have to worry about finding fuel all the time. (my current aircraft is avgas only, which has become a struggle to source in places like smaller airfields in italy or norway)

reading through the many posts and suggestinos here on the forum i've diceded that sloshing with the caswell sealer. they seem to be the only product that is really designed to go into fibreglass tanks as well and 2k is a must in my oppinion when it comes to sovlent resistancy. since the wings are not on the airplane at the moment i plan on just turnging it in all directions together with a helper in order to apply the stuff.

my questions for those that went through the process already:

- is that stuff liquid enough that i can get a good feeling when we shake that wing in order to get it in touch with all the various surfaces in the "chambers" of the fuel tanks or should i go for a colored option so that i can inspect the tank afterwards with a borescope to see if it really is covered in caswell? would prefer the transparent one to keep the gas level visible at the wing root.

- does anyone have long term experience with it? i saw some posts from several years ago and was hoping a few of you could gibe us an update on how it's holding up.

the only viable alternative i see to sloshing would be to open up the underside of each section and then paint the tank with some sealant (maybe even apply the same caswell sealer if sloshing is the problem). i have to say i like the way how Chris did it but would prefer sloshing as it seems a lot less work (and i've got enought other stuff to do to finish this airplane)

 

[1avidflyer 1983]

I've sloshed tanks with KBS coatings and it seemed to flow very well.  I put the wings into wing rotators and was able to spin them around fairly easy. JImChuk

[marksires 484]

I don't recommend sloshing, period.  It will eventually separate from the tank wall and clog your fuel system.  It may take 5-10 years, but it will eventually ruin your day.  The problem is there is no way to properly prepare the interior surface so it can adhere properly.  Would you paint your cowl without sanding it first?

[wypaul 448]

I did my tanks before installing several years ago, used the acetone then Caswell and no problems.  Caswell isn't sloshing per se, but a true Epoxy made for this very purpose.  Another fellow here just recently did his wing tank that was installed and used for several years.  He removed the wing and a buddy helped him rotate it and then inspected it with a bore scope.  Fixed the leak and is doing good.  I recommend buying one kit for each wing because the mix is critical. 

I think you can expect a great outcome with a little diligence!

[kitfoxjunky 4]

I did my tanks before installing several years ago, used the acetone then Caswell and no problems.  Caswell isn't sloshing per se, but a true Epoxy made for this very purpose.  Another fellow here just recently did his wing tank that was installed and used for several years.  He removed the wing and a buddy helped him rotate it and then inspected it with a bore scope.  Fixed the leak and is doing good.  I recommend buying one kit for each wing because the mix is critical. 

I think you can expect a great outcome with a little diligence!

I talked to Caswell, and they did not recommend using acetone on fiberglass tanks.  Hot water and detergent only. The acetone can attack the fiberglass resin.  My tanks in my Kitfox IV, which I  have had for 20 years, started leaking recently. Caswell looks like a fit, as I am just trying to get through the summer before I upgrade to the larger tanks, but my understanding is that even the small 6 gal wing tank has baffles in it to stop fuel from sloshing around in flight.  How can you get the Caswell to flow around the baffles? 

[wypaul 448]

The KF that I referred to had 13 gallon tank which have several baffles.  The key is to raise and lower the ends of the wing alternately while rotating the wings and using the excess amount of the Caswell Epoxy. The excess is then poured from the tank. If you would like to talk to the fellow that did it in his KF message me, I believe he would be open to talking with you on the phone. 

As far as the acetone goes use your own judgement.  The screws I used but my tanks were not installed yet.  I would probably opt not to use them in an installed wing for fear of not getting them all out.

[ChrisBolkan 130]

I recommend cutting into the bottom of the tank, finding the leak, repair it with grey polysulfide sealer and riveting a cover over the hole with pink polysulfide sealer. i have done this on two wings and a friend has also. Results in a solid fix that can be accessed again if required. If you are dealing with a leak, on both my friend's and my tank it was at the rear spar wing root area, accessible by just cutting into one bay.

http://avidfoxflyers.com/index.php?/topic/738-wing-tank-repair/#comment-4555

Edited 30 Apr 2020 by ChrisBolkan